Measuring Ions Per Bunch in the RFQ

The 6He-CRES collaboration centered at the University of Washington is focused on finding beyond-the-standard-model physics contributions to the electroweak interaction. Current understanding of ions traps suggest that our radio frequency quadrupole (RFQ) is limited to 104 ions per bunch, but from simulations it predicts yields of 106 ions per bunch. The next stage of the collaboration’s experimental program is to implement an ion trap to reduce systematics affecting their current setup. The motivation for getting 106 comes from the low statistics expected from smaller bunch sizes. The planned upgrade will allow for several experiments to be done with different sources in a reasonable timeframe. To experimentally find the space-charge limit of the RFQ, we will be sending potassium ions through an RFQ with low intensity and slowly increase the gain of the source until the RFQ becomes saturated with ions. By experimentally showing that it is possible to achieve 106 ions per bunch, we will show that an ion trap addition to the 6He-CRES experiment will not be at the trade-off of a great loss in count rate. We sought to measure the potential bunch size by changing several parameters to change the bunch size without greatly increasing our beam spread. The results that will be shown will contribute to the future direction of the collaboration.